This present invention relates to techniques for fabricating flat panel displays. More particularly, the invention is illustrated in an example related to the manufacture and repair of a color filter for use in a flat panel display such as an active matrix liquid crystal display (AMLCD) or the like. But it will be recognized that the invention also can be applied to the manufacture of almost any type of color filter media or pixels using a photolithography technique, for example.
The use of a flat panel display such as an active matrix liquid crystal display (AMLCD) or the like continues to grow rapidly. For example, consumer items such as a pocket TV, a notebook computer, an engineering work-station, a high-definition television (HDTV), and others use such a display. Based upon the continued demand for this display, industry has made massive capital investments in creating state-of-art manufacturing lines.
Color flat panel displays are merely an example of a flat panel display, which is being used extensively in computers. These flat panel displays often use color filters to provide the color to the display image. Color filters are generally made using printing-type processes, which are often difficult and costly.
Unfortunately, the color filters are often plagued with defects or anomalies, which are introduced during the manufacturing process. These anomalies include, for instance, inclusions in the color medium and color non-uniformity. Inclusions can be found in the color medium or coating layer. They are often portions of photoresist, particulates, or voids, which define themselves in the color filter. Non-uniform color can be caused by an "overabundance" of color filter material in a pixel. For instance, a red color pixel may have an excessive thickness, which appears to create a deeper or darker display color in relation to surrounding pixels upon illumination. Alternatively, non-uniform color is often caused by a thinner region of color filter material in a pixel. This thinner region appears to lack color or appears "washed out" in relation to surrounding pixels. Furthermore, mask portions may remain on the color filter material where the mask portions block.
A few techniques have been proposed or used to eliminate some of these anomalies. In particular, polishing or grinding tools have been used to remove an overabundance of color filter material from a pixel. These polishing tools generally have a rotatable pad member, which is abrasive. By way of rotation and pressure placed against the color filter material, portions of the overabundant or thicker color filter material are physically removed. These techniques, however, often require great precision to remove a desired amount of color filter material, which often causes a potential for additional damage to the color filter material. Additionally, as pixel sizes decrease, it becomes more difficult to accurately remove color filter material from a pixel.
Anomalies such as portions of photoresist, particulates, or voids generally cannot be removed to repair the color filter. In most cases with enough severity, the color filter plate is rejected and discarded, which is generally expensive and inefficient. As much as 30% of filters manufactured must be discarded due to such defects. Accordingly, the cost of flat panel displays using color filters is often significantly more expensive than other types of displays. In fact, the color filter represents one of the higher cost components of the display. A large portion of these costs is associated with the large number of displays that are rejected due to anomalies, which are introduced into the color filter during the manufacturing process.
From the above, it can be seen that a technique for repairing color filters or removing anomalies from color filters that is easy, cost effective, and reliable is often desirable.